Holbein's work in Basel during the decade of 1515–25 was extremely varied, if also sometimes derivative. Trips to northern Italy (c. 1517) and France (1524) certainly affected the development of his religious subjects and portraiture, respectively. Holbein entered the painters' corporation in 1519, married a tanner's widow, and became a burgher of Basel in 1520. By 1521 he was executing important mural decorations in the Great Council Chamber of Basel's town hall.

Holbein was associated early on with the Basel publishers and their humanist circle of acquaintances. There he found portrait commissions such as that of the humanist scholar Bonifacius Amerbach (1519). In this and other early portraits, Holbein showed himself to be a master of the current German portrait idiom, using robust characterization and accessories, strong gaze, and dramatic silhouette. In Basel, Holbein was also active in designing woodcuts for title pages and book illustrations. The artist's most famous work in this area, a series of 41 scenes illustrating the medieval allegorical concept of the “Dance of Death,” was designed by him and cut by another artist as early as about 1523 to 1526 but was not published until 1538. Its scenes display an immaculate sense of order, packing much information about the lifestyles and habits of Death's victims into a very small format. In portraiture, too, Holbein's minute sense of observation was soon evident. His first major portrait of Desiderius Erasmus (Erasmus, Desiderius) (1523) portrays the Dutch humanist scholar as physically withdrawn from the world, sitting at his desk engaged in his voluminous European correspondence; his hands are as sensitively rendered as his carefully controlled profile.

Protestantism, which had been introduced into Basel as early as 1522, grew considerably in strength and importance there during the ensuing four years. By 1526 severe iconoclastic riots and strict censorship of the press swept over the city. In the face of what, for the moment at least, amounted to a freezing of the arts, Holbein left Basel late in 1526, with a letter of introduction from Erasmus, to travel by way of the Netherlands to England. Though only about 28 years old, he would achieve remarkable success in England. His most impressive works of this time were executed for the statesman and author Sir Thomas More (More, Sir Thomas) and included a magnificent single portrait of the humanist (1527). In this image, the painter's close observation extends to the tiny stubble of More's beard, the iridescent glow of his velvet sleeves, and the abstract decorative effects of the gold chain that he wears. Holbein also completed a life-size group portrait of More's family; this work is now lost, though its appearance is preserved in copies and in preparatory drawing. This painting was the first example in northern European art of a large group portrait in which the figures are not shown kneeling—the effect of which is to suggest the individuality of the sitters rather than impiety.

Before Holbein journeyed to England in 1526, he had apparently designed works that were both pro- and anti-Lutheran in character. On returning to Basel in 1528, he was admitted, after some hesitation, to the new—and now official—faith. It would be difficult to interpret this as a very decisive change, for Holbein's most impressive religious works, like his portraits, are brilliant observations of physical reality but seem never to have been inspired by Christian spirituality. This is evident in both the claustrophobic, rotting body of the Dead Christ in the Tomb (1521) and in the beautifully composed Family of Burgomaster Meyer Adoring the Virgin (1526). In this latter painting, Holbein skillfully combined a late medieval German compositional format with precise Flemish realism and a monumental Italian treatment of form. Holbein apparently quite voluntarily gave up almost all religious painting after about 1530.

In Basel from 1528 to 1532, Holbein continued his important work for the town council. He also painted what is perhaps his only psychologically penetrating portrait, that of his wife and two sons (c. 1528). This picture no doubt conveys some of the unhappiness of that abandoned family. In spite of generous offers from Basel, Holbein left his wife and children in that city for a second time, to spend the last 11 years of his life primarily in England.

In an analogous fashion, Holbein's mature portraits present an intriguing play between surface and depth. The sitter's outlines and position within the frame are carefully calculated, while inscriptions applied on the surface in gold leaf lock the sitter's head into place. Juxtaposed with this finely tuned two-dimensional design are illusionistic miracles of velvet, fur, feathers, needlework, and leather. Holbein acted not only as a portraitist but also as a fashion designer for the court. The artist made designs for all the state robes of the king; he left, in addition, more than 250 delicate drawings for everything from buttons and buckles to pageant weapons, horse outfittings, and bookbindings for the royal household. This choice of work indicates Holbein's Mannerist concentration on surface texture and detail of design, a concern that in some ways precluded the incorporation of great psychological depth in his portraits.

Holbein was one of the greatest portraitists and most exquisite draftsmen of all time. It is the artist's record of the court of King Henry VIII of England, as well as the taste that he virtually imposed upon that court, that was his most remarkable achievement.

The fact that Holbein's portraits do not reveal the character or spiritual inclinations of his sitters is perfectly paralleled by knowledge of the artist's life. His biography is basically a recounting of disparate facts; about his personality practically nothing is known. Not one note or letter from his own hand survives. Other men's opinions of him are often equally inscrutable. Erasmus, one of Holbein's most renowned sitters, praised and recommended him on one occasion but scorned the artist as opportunistic at another time. Indeed, Henry VIII, who sent Holbein to the Continent to help select a bride by providing a dependable portrait for his scrutiny, was perhaps the only person who had absolute confidence in Holbein.

The artist's detachment and his refusal to submit to an authority that might inhibit his own creative (but very worldly) powers enabled him to produce paintings whose beauty and brilliance have never been questioned. Had he been a more devout Christian or more subject to the turmoil of his times, his artistic achievement might have been quite different. In recent times the lack of spiritual involvement in his work has been consistently noted, especially inasmuch as the 16th century was a time when few artists managed to remain above the religious conflict sweeping Europe. Thus, the effect of Holbein's art has often been felt to be more artistic and external than expressionistic or emotional. Only in that sense, however, is his achievement finally limited.